Macular degeneration is caused by the deterioration of the central portion of the retina, the inside back layer of the eye that records the images we see and sends them via the optic nerve from the eye to the brain. The retina's central portion, known as the macula, is responsible for focusing central vision in the eye which controls our ability to read, drive a car, recognize faces or colors, and see objects in fine detail.
Age related macular degeneration (AMD) is the leading cause of legal blindness among people over 65. Persons suffering from AMD lose the ability to see fine details. The patient is able to see the edges of an image but the middle of the image is blank or appears as a dark spot called a scotoma. This condition can occur in one or both eyes.
There are two basic forms of AMD, known as “wet AMD” and “dry AMD”. Dry AMD is also referred to as non-neovascular or non-exudative AMD. Approximately 85% to 90% of patients with AMD have the dry (atrophic) type AMD. Patients with this form AMD may have good central vision (20/40 or better) but substantial functional limitations. In dry AMD, the deterioration of the retina is associated with the formation of drusen under the macula. Drusen are accumulations of acellular (small yellow deposits), amorphous debris subjacent to the basement membrane of the retinal pigment epithelium. This phenomena leads to a thinning and drying out of the macula, causing the macula to lose its function. Currently, there is no known cure for Dry AMD and no approved pharmacological treatment for the condition. A strong need therefore exists for a treatment that reduces or limits macular degeneration.
Prostaglandins (hereinafter, referred to as PG(s)) are members of class of organic carboxylic acids, which are contained in tissues or organs of human or other mammals, and exhibit a wide range of physiological activities. PGs found in nature (primary PGs) have, as a general structural property thereof, a prostanoic acid skeleton as shown in the formula (A):

On the other hand, some of synthetic analogues of primary PGs have modified skeletons. The primary PGs are classified to PGAs, PGBs, PGCs, PGDs, PGEs, PGFs, PGGs, PGHs, PGIs and PGJs according to the structure of the five-membered ring moiety, and further classified into the following three types by the number and position of the unsaturated bond at the carbon chain moiety:
Subscript 1: 13,14-unsaturated-15-OH
Subscript 2: 5,6- and 13,14-diunsaturated-15-OH
Subscript 3: 5,6-, 13,14-, and 17,18-triunsaturated-15-OH.
Further, the PGFs are classified, according to the configuration of the hydroxyl group at the 9-position, into α type (the hydroxyl group is of an α-configuration) and β type (the hydroxyl group is of a β-configuration).
In addition, some 15-keto PGs (i.e. those having an oxo group at position 15 in place of the hydroxy group) and 13,14-dihydro (i.e. those having a single bond between positions 13 and 14) -15-keto-PGs are known as substances naturally produced by enzymatic actions during in vivo metabolism of primary PGs and have some therapeutic effect. For example, 15-keto-prostaglandin compounds have been known to be useful for the treatment of ocular hypertension and glaucoma (U.S. Pat. Nos. 5,001,153 and 5,151,444, These publications are incorporated herein by reference).
However it is not known how the 15-keto-prostaglandin compound acts on macular degeneration, especially AMD, more especially dry AMD.